Arenal volcano is the most spectacularly active in Costa Rica. Hotels in the region tout their views of the lava flows and red hot boulders ejected from the volcano glowing in the darkness. Although eruptions are the main attraction, you should be aware that even in the dry season the clouds sometimes obscure the top of the volcano, and your chances of seeing a pyroclastic display are lessened in the rainy season. Volcano watching is better than a fifty-fifty proposition, but you should plan on taking advantage of some of the other attractions in the area, and consider it a bonus if you see Arenal put on a huge display. These tips will also help you maximize your chances of seeing a big pyroclastic show.

Arenal Volcano puts on a fiery display under a full moon.

The perfect cone is visible from most anywhere in the area, but if you want a good view of an eruption, your best bet is to stay in one of the "observatory" type lodges, and stay up late or get up with the sun. The clouds tend to move in soon after sunrise. There were hiking tours based out of La Fortuna de Arenal which used to take you up the west ridge to the the crater rim. Because of the number of people killed by ash, falling cinders and toxic fumes, this is no longer allowed. There are still plenty of hiking trails that get you as close as is advisable.

Chato volcano—this extinct volcano (last erupted a little over 5,000 years ago) has a lopsided crater that cradles a small lake and can be accessed by a hiking trail starting near the Arenal Observatory lodge.

Volcán Arenal had its largest eruption in modern times in 1968, blasting lava and molten boulders from three separate craters to form a new one, knocking nearly 165 feet (50 meters) off the elevation, and destroying the villages of Tabacón and Pueblo Nuevo killing all of the inhabitants. Since then it has had continuous activity, and large eruptions in 1973, 1975, 1993, 2000, 2003, and 2005. Fatalities have been limited to tourists and guides that wandered too close.